A sugar-laden muesli bar endorsed by the Heart Foundation is deceptive, a Wellington father has complained to the Commerce Commission.

Ruben Blok bought a box of Tasti Fruitsies - which have a Heart Foundation red tick - for his children, aged 1 and 4.

"It's a muesli bar, you don't expect it to be mega-healthy, but geez, almost 50 per cent sugar, that's criminal," he said.

The Paraparaumu man checked the nutrition label after tasting how sweet the bar was and found it had 44 grams of sugar per 100g, on a par with popular chocolate bars.

"If the labelling was not so deceiving, and it was correctly filed in the confectionary section, I would not have purchased it."

Wellington dietitian Sarah Elliot said muesli bars should be treated as a "sometimes" food.

"Muesli bars are glorified chocolate bars. On the whole, if you think about the fact that 50 per cent of our population is either overweight or obese, it's not a food that we're promoting for everyday."

Muesli bars should be below 600 kilojoules, have less than 10 grams of sugar and less than 2g of saturated fat, she said.

The Commerce Commission confirmed it had received a complaint from Mr Blok, but a spokeswoman said it would not be investigating.

More than 1100 supermarket products carry the heart tick, including pizza, pies and flavoured milk. Each food category has its own criteria and manufacturers pay for the tick by passing on a slice of their sales to the Heart Foundation.

Mr Blok said he was not critical of Tasti, but rather of the foundation for endorsing the bars.

Putting the tick on a sugary bar "tarnished" the reputation of the foundation.

"They don't take sugar into account as a criteria . . . that blew my mind. Perhaps they do not consider the obesity epidemic a health or heart problem."

Nine cereal bars on supermarket shelves have the Heart Foundation tick. Levels of sodium, kilojoules and fat have to meet certain criteria and the bars have to contain at least 1.5 grams of fibre per serving.

The amount of sugar is not considered because there was "no scientific evidence that sugar causes heart disease", foundation tick manager Deb Sue said. "Just because something's high in sugar doesn't automatically make it bad food."

Criteria for each food category were created by a panel of food technologists and dietitians, and ticks made it easy for people to choose healthier options, she said.

Tasti told Mr Blok in a letter that a "large percentage" of sugar in its Fruitsies bars were from dehydrated fruit puree.

Milo dropped the red tick from its packaging in 2009 after an outcry from nutritionists, who said the drink was half sugar.